The service and repair of the lens units of a railway light signal have always been a problem in the railway signal industry. Each time a lens unit is serviced the signal must be re-aligned and re-focused before it is re-activated. This is both costly and time consuming. Hence, it would be highly desirable to design a light signal that could be maintained without alignment or focusing thereof.
Some conventional light signals require that the maintainer or maintenance person reach around the background to remove the outer lens components and then the entire lens unit. The problem with this method is that it is very difficult and dangerous to reach around the outer lens components. Furthermore, each installed lens unit needs to be re-focused.
Still other devices require that the maintenance person turn the signal head on the mast to gain access to the outer lens components and thus the entire lens unit. The obvious problem with this approach is that the signal head needs readjustment during servicing which is rather cumbersome and costly.
In most instances a platform must be built in front of the signal case so that the maintenance person can have access to the front of the signal. These platforms require significant amounts of time and money to construct. It would therefore be highly desirable to design a signal device that does not require servicing through the front of the device.
Conventional light signals typically consist of three aspects or lens units that are bolted together within a single case. Thus, whenever a lens unit is being repaired or replaced the entire lens unit must be removed from its scaffolding and returned to a maintenance facility where the individual lenses are re-focused and re-aligned in a dark room. This increases the cost and repair time required for servicing each lens unit.
Many conventional light signal cases also require that the lens units be mounted by means of a series of aluminum rings that sandwich the lens. These rings are bolted to a machined surface on the front of the signal case. In the present light signal, a lens mount, in the form of a ring, is mounted to the machined fixed or immovable inside surface of the case to provide for retention of the lens unit. Accordingly, no access to or through the front of the light signal is required. In other words, in accordance with the present invention, access only from the rear permits removing all significant elements requiring replacement or repair and, hence, obviates the need for a maintenance man to do anything affecting the front of the light signal case.
Many light signals require that the lamp or lamp filament be focused into position at or near the focal point of the lens unit each time the lamp holder or receptacle is assembled into the light signal. The present signal head is constructed so that the filament lamp is automatically positioned close enough to the focal point of the lens unit to provide adequate range and light output and thereby avoid the need for focusing. Accordingly, the time and expense of a focusing procedure and focusing equipment are avoided.
The aforementioned methods are dangerous since they typically require access through the front of the light signal. Still other signals need a platform built thereabout in order to perform simple maintenance procedures or readjustment of the mast head. More importantly, however, the light signal cases discussed above all require re-alignment and/or re-focusing of the lamp and lenses each time maintenance work is done.
Against the foregoing background, the present inventors have designed a novel light signal casing wherein access to each lens unit of the light signal is effected through the rear of the light signal's case. This allows maintenance personnel to replace the lens mount or bezel and/or the outer lens without the need to access the interior of light signal through the front thereof.
It also provides a new light signal in which the case or housing of the light signal provides precise aspect to aspect alignment.
The present invention provides a unique light signal in which lens units are fixed or automatically focused.
The present invention further provides a light signal in which the case is divided into individual lens compartments to ensure accurate indications by avoiding phantom indications and, thereby, assuring proper aspect to aspect alignment.
Furthermore, the present invention provides a light signal in which the case provides strength and weather protection for the components inside the case.